It is, of course, well known to incorporate thrust reversal means on jet engines to effect deflection of the exhaust efflux of the engine in a generally forward direction and provide aerodynamic braking during landing (i.e., after touch-down). Typically, thrust reversal means for jet engines takes the form of large, so-called deflector or clamshell doors mounted aft of the engine thrust nozzle, which doors are movable into the path of the engine exhaust gases to deflect them forwardly. In certain cases, the deflector doors pivot into positions where they protrude beyond the engine nacelle and can cause an engine backpressure problem at high forward speeds and low throttle settings. Protruding doors of this type are aerodynamically unsafe and cannot be used for inflight deployment to improve steep descent and glide slope control capabilities.
In an effort to utilize the thrust reversing capabilities for ground and for inflight deployment, cascade/clamshell thrust reversers have been devised in which the clamshell door or doors themselves do not protrude beyond the engine nacelle, even when in the thrust-reversing position. In this type of reverser, the exhaust gases from the jet engine are directed through a cascade of vane members in the nacelle wall. If the clamshell doors are pivoted about a single pivot point, as is usual, problems arise in that the single pivoting door does not expose sufficient open area and has a tendency to wipe through the area where the cascade of vane members should be located.